1. Field of the Invention
The present invention relates to a fuel state sensing device that senses a mixing state of air into fuel.
2. Description of Related Art
Concerning fuel supply of fuel used for combustion in an internal combustion engine, there has been known a fuel supply system that supplies the fuel in a tank to a common rail (pressure accumulator) with a high-pressure pump and that performs distribution supply of the fuel accumulated in the common rail to injectors of respective cylinders, thereby injecting the fuel from the injectors (refer to Patent document 1: JP-A-2009-74535).
If a fuel supply route extending from the tank to the injector is obstructed slightly, for example, because a filter provided in the fuel supply route clogs, there is a case where air mixes in the fuel having passed through a narrowed part, at which the fuel supply route is slightly obstructed. It is thought that the mixing of the air occurs because an air component contained in the fuel deposits when the air component passes through the narrowed part (clogged part). It is also thought that the mixing of the air is caused when a damage such as a crack exists in a pipe constituting the fuel supply route and the air mixes into the fuel through the damaged part. If such the deposition and mixing of the air occur and an air quantity mixing into the fuel increases, problems such as extreme decrease in an actual fuel injection quantity as compared to a target fuel injection quantity arise.
However, presently, there is no means to sense an air mixing quantity or an air mixing ratio to the fuel. Therefore, it is difficult to detect deterioration of controllability of the fuel injection quantity.